Open AccessOverexpression of wbkF gene in Brucella abortus RB51WboA leads to increased O-polysaccharide expression and enhanced vaccine efficacy against B. abortus 2308, B. melitensis 16M, and B. suis 1330 in a murine brucellosis model
Author(s) -
Neha Dabral,
Grant N. Burcham,
Neeta Jain-Gupta,
Nammalwar Sriranganathan,
Ramesh Vemulapalli
Publication year - 2019
Publication title -
plos one
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.99
H-Index - 332
ISSN - 1932-6203
DOI - 10.1371/journal.pone.0213587
Subject(s) - virulence , microbiology and biotechnology , biology , brucella melitensis , complementation , isotype , virology , antigen , strain (injury) , attenuated vaccine , brucella , antibody , gene , mutant , monoclonal antibody , immunology , brucellosis , biochemistry , anatomy
Brucella abortus RB51 is an attenuated, stable, spontaneous rough mutant derived in the laboratory from the virulent strain B . abortus 2308. Previous studies discovered that the wboA gene, which encodes a glycosyltransferase required for synthesis of the O-polysaccharide, is disrupted in strain RB51 by an IS 711 element. However, complementation of strain RB51 with a functional wboA gene (strain RB51WboA) does not confer it a smooth phenotype but results in low levels of cytoplasmic O-polysaccharide synthesis. In this study, we asked if increasing the potential availability of bactoprenol priming precursors in strain RB51WboA would increase the levels of O-polysaccharide synthesis and enhance the protective efficacy against virulent Brucella challenge. To achieve this, we overexpressed the wbkF gene, which encodes a putative undecaprenyl-glycosyltransferase involved in bactoprenol priming for O-polysaccharide polymerization, in strain RB51WboA to generate strain RB51WboAKF. In comparison to strain RB51WboA, strain RB51WboAKF expressed higher levels of O-polysaccharide, but was still attenuated and remained phenotypically rough. Mice immunized with strain RB51WboAKF developed increased levels of smooth LPS-specific serum antibodies, primarily of IgG2a and IgG3 isotype. Splenocytes from mice vaccinated with strain RB51WboAKF secreted higher levels of antigen-specific IFN-γ and TNF-α and contained more numbers of antigen-specific IFN-γ secreting CD4 + and CD8 + T lymphocytes when compared to those of the RB51 or RB51WboA vaccinated groups. Immunization with strain RB51WboAKF conferred enhanced protection against virulent B . abortus 2308, B . melitensis 16M and B . suis 1330 challenge when compared to the currently used vaccine strains. Our results suggest that strain RB51WboAKF has the potential to be a more efficacious vaccine than its parent strain in natural hosts.